EP 0 475 382 A1 to the present applicant discloses such a method using shoring devices with supports. Here, there is proposed a method of lining or shoring deep trenches by means of support frames which can be set up at equal spacings in the longitudinal direction of the trench. The support frames are composed of two parallel supports and a flexurally stiff spreading frame which connects the supports and holds them at a spacing and which is displaceable along the supports. In that document the spreading frames are referred to as ‘stiffening frames’. Each support frame forms a support structure which is particularly advantageous in terms of handling in installation and removal. Large-area shoring panels or plates are guided displaceably in receiving passages disposed at both sides of the supports, wherein the shoring panels can be introduced with their lateral edges. The support frames and the shoring panels are pushed or lowered into the trench alternately as the trench is dug out.
In that case the spreading frame is preferably guided on the supports displaceably between a lower abutment and an upper abutment, wherein the lower abutment is arranged at least at the height of the necessary excavator bucket freedom of between about 1 and 1.50 m from the support base and the upper abutment is arranged at a spacing from the lower abutment, which corresponds to the height of the spreading frame, for example 1.75 m, and a permissible support advance, for example 0.5 m. After the support frame has been set up and lowered to a level at which the upper edge of the spreading frame is at the height of the edge of the trench the upper abutments can be removed and a second spreading frame inserted into the supports of the support frame. The upper abutments can then be fixed to the supports at a spacing above that second spreading frame. Optionally, a third flexurally stiff support frame can also be introduced into the supports of the spreading frame. The spreading frames can be connected together for the retreat movement of the support frame.
Those shoring devices have proven their worth in particular for shoring trenches of a great depth of 8 m and more. In comparison with the prior spreading struts which were connected pivotably between the supports of a support frame, the use of a flexurally stiff spreading frame has the crucial advantage that the points of force transfer from the supports to the spreading frames upon a relative movement of the two supports of the pair of supports relative to each other remain within a perpendicular plane extending in the longitudinal direction of the trench. The supports are consequently displaceable relative to each other and relative to the spreading frame in a vertical plane. The shoring panels, the edges of which are guided in vertical receiving passages in the supports also remain in a vertical plane extending in the longitudinal direction of the trench, upon relative movements of the components of the shoring device relative to each other. Thus, when relative movements occur, there is no displacement of the supports or the shoring panels transversely with respect to the longitudinal direction of the trench. Such transverse movements are highly detrimental as they lead to an increased application of force upon movement of those elements, vibration and tremors in the adjoining earth and settlement phenomena in the adjoining earth. The tremors and settlement phenomena introduced into the adjoining earth in that way can seriously damage adjacent building structures. Such transverse movements are effectively and completely avoided by the described shoring device.
Eliminating the transverse movements makes it possible to use very long supports which are suitable for receiving a plurality of shoring panels and permit shoring of particularly deep trenches. Thus outer and inner shoring panels are guided in the receiving passages of the supports of EP 0 475 382 A1 so that a second pair of mutually opposite shoring panels is passed through between the first pair of shoring panels and inserted into the trench. The inner shoring panels are guided displaceably past the outer shoring panels and in the installed condition of the shoring device are in the lower portion of the trench whereas the outer shoring panels are in the upper portion of the trench. The trench is consequently of a stepped cross-section. Furthermore, both in the case of the outer shoring panels and also the inner shoring panels, it is possible to arrange on what are referred to as base panels of a first height (for example 2.35 m) fitment panels of a second height (for example 1.35 m) arranged between two successive supports, in which case the base panel and the fitment panel are respectively fixedly joined together. The total height of the shoring panels is then about 7.40 m.
Systems discussed herein may also be used in connection with a trench shoring device in which the supports are not separate components to which the plates are vertically displaceably fixed, but those in which the supports or the linear guides are rigidly fixed to the plates or integrated into the plates. DE 42 26 405 A1 in which the applicant is listed as inventor describes and shows in FIG. 2 such a device in which the supports having the linear guide are welded to the vertical edges of the shoring panel. Such shoring panels with linear guides, arranged at the two vertical edges, for the spreading frames generally form individual shoring arrays or shoring boxes. A shoring array comprises two mutually opposite shoring panels and two spreading frames which are guided on the one hand between the front edges of the two shoring panels and on the other hand between the rear edges of the two shoring panels. In addition it is possible to provide what is referred to as a head shoring, that is to say a head plate which extends transversely relative to the trench and which is supported against the front edges and a head plate which is supported against the rear edges of the two shoring panels.
A large number of different procedures for achieving great trench depths have been proposed in the state of the art. Thus the documents DE 32 43 122 A1, DE 26 54 229 A1, DE 23 02 053 B2 and FR 2 222 867 disclose two supports displaceable relative to each other in their longitudinal direction on each side of the trench. A single shoring panel is held in each of those supports. The supports are held at a spacing by spreading struts which are either hingedly fixed to the supports or, as in the case of DE 23 02 053 B2, are guided on the supports displaceably by way of spreading heads. When a support of a pair, upon installation or removal of the shoring device, is moved vertically with respect to the other support, then the spreading struts always perform a tilting movement about the longitudinal axis of the trench. That causes a reduction in the spacing between the spreader ends and thus between the supports of the pair of supports. Even if the spreading heads are guided displaceably on the supports the spreading struts perform a tilting movement under load because of the friction of the spreading heads in the guides of the supports. For that reason only small relative movements between the supports of a pair are permissible and the inclination of the spreading effect may not be more than 5° relative to the horizontal. Apart from the fact that in practice those limits are not always observed, even slight changes in the spacing between the supports of a pair have the result that the supports and the shoring panels can only be moved with very great difficulty and that settlement phenomena occur in the adjoining ground and endanger the adjoining buildings and structures (pipes, conduits etc).
In addition those shoring devices are generally installed simultaneously on each side with both mutually displaceable individual supports. In other words, both individual supports are placed on the earth and after the trench has been dug out to a certain depth of the trench are pressed into the ground. The trench can only be dug out within the supports and the shoring panels as the excavator bucket does not reach the earth beneath the supports and the shoring panels. The earth under the supports and the shoring panels is cut away by the lower edge of those elements when they are pushed in and drops into the interior of the trench. For that reason the lower edges of the supports and shoring panels extend inclinedly and form a cutting edge which pushes the earth inwardly upon being moved downwardly (see DE 32 43 122 A1). As the supports are generally fitted simultaneously in the known shoring devices, the outer support, upon being pushed into the ground, must displace not just the earth under its cross-section but also the earth beneath the inner support, inwardly of the trench. This means that very high forces are required to press the supports into the ground. The requirement for cutting away ground of double the support width means that the forces become so high that either they overload the support material or they cannot be applied by usual construction equipment.
DE 32 43 122 A1 describes a shoring device having a first pair of supports and a second pair of supports. The supports of the second pair bear against the insides of the supports of the first pair and are linearly guided thereat. At the supports of the first pair, the edges of upper and outer shoring panels are guided displaceably. The edges of lower and inner shoring panels are guided displaceably at the supports of the second pair. The upper outer supports of the first pair are held at a spacing above the lower inner supports of the second pair by a spreading strut—referred to as a transverse strut in DE 32 43 122 A1. Two transverse struts between the lower inner supports hold the inner supports at a spacing and press them against the outer supports. When the inner supports are not present the support frame formed solely by the outer supports is unstable. When shoring deep trenches it is therefore necessary for the upper outer supports of the first outer shoring device to be fitted into the trench only together with the lower inner supports of the second inner shoring device. Furthermore, that operation of inserting the outer and inner supports must be effected pair-wise so that very high weights have to be lifted and moved. In addition the lower support must be shorter than the upper one in order to be able to be inserted beneath the spreading strut between the supports of the upper pair.
For those reasons shoring devices with two individual supports which are displaceable vertically relative to each other and which have the linear guides disposed on each side of the trench have not proven satisfactory in the past. For shoring deep trenches, use is primarily made of the above-described shoring devices with supports which are held at a spacing by a displaceable spreading frame, in which upwardly disposed outer and downwardly disposed inner shoring panels are guided displaceably for forming a stepped cross-section. By virtue of the above-described avoidance of transverse movements upon installation and in the retreat mode, those devices, as mentioned, avoid adverse effects on the adjoining ground.
Accordingly, it would be desirable to develop a method of trench shoring in such a way that, with simple insertion and removal of the shoring device used in this respect, it is possible to line trenches of great depth. It would also be desirable to develop the elements of a device for trench shoring in such a way as to permit shoring of trenches of great depth.